Optimal reorientation of spacecraft using only control moment gyroscopes

Spacecraft reorientation can require propellant even when using gyroscopes since these have momentum saturation limits at which control is lost until thrusters are fired to desaturate them. To eliminate this need and thereby reduce cost, this work seeks trajectories that avoid saturation altogether by taking advantage of known disturbance torques. This concept is formulated as an optimal control problem and a direct transcription method is applied to obtain numerical solutions. Unlike recent related work on attitude maneuvers and momentum desaturation using only gyroscopes, this thesis allows the full rotational state (attitude, rate, and momentum) at the start and end of the maneuver to be specified. This thesis establishes the viability of this technique, which can potentially extend the operational lifetime of any gyroscope-equipped spacecraft, by successfully demonstrating it in a flight test in which the International Space Station was rotated 90 deg without propellant